Future generations wonder: Wait, what did 'XP' stand for again?
Screenshot from Wikipedia
If you want to find an archaic outdated operating system, maybe you need look no further than your desktop: after all, it's possible your PC is one of the 40.7% that still runs Windows XP. This is an operating system that was released in October of 2001 -- ten and a half years ago, as of this writing. To give you a sense of how long that span of time is (and to make you feel really old), ten and a half years before Windows XP was released was April of 1991, when Windows 3.0 was Microsoft's reigning operating system. Windows NT wouldn't be released for another two years. XP's been with us for an eternity, in computer terms.
It may not be quite fair to call Windows XP a "decade-old operating system" -- it was after all the top of the line until Windows Vista was released, though even that was five years ago. Still, with such an impressively large installed base, it's a good bet that an article like this one written five or ten years from now will include "ancient x86 box running Windows XP" in its rogues gallery.
Also by Josh Fruhlinger:
Where did I come from? The origin(s) of my MacBook Pro
Six crucial tech companies you've never heard of
Ahead of their time: Nine technologies that came early
Curious histories of generic domain names